The newly developed Mechanochemical Endovenous Ablation (MOCA) device uses a technique that combines mechanical endothelial damage using a rotating wire with the infusion of a liquid sclerosant. Heating of the vein and tumescent anesthesia are not required; only local anesthesia is utilized at the insertion site. Previously we showed that endovenous MOCA, using polidocanol, is feasible and safe in the treatment of great spahenous vein (GSV) incompetence. However, larger studies with a prolonged follow-up to prove the efficacy of this technique in terms of obliteration rates are lacking. This randomized trial was designed to compare occlusion rate, post-operative pain and complications between radiofrequency ablation (RFA: the current treatment for GSV incompetence) en MOCA.